A thin film transistor (TFT) array substrate can be used in a liquid crystal display (LCD) and an organic light emitting device (OLED). A liquid crystal display generally comprises a thin film transistor array substrate, a color filter substrate and a liquid crystal layer interposed between these two substrates. When an electric field is formed between the two substrates, orientation of liquid crystal molecules varies to change light transmittance for displaying an image. A organic light emitting display device displays an image by using an organic electroluminescent material. A pixel of the organic light emitting display device generally comprises a driving thin film transistor for providing current to the organic electroluminescent material and a switch thin-film transistor for controlling the driving thin film transistor to be turned on or off.
These display devices may comprise gate lines and data lines to drive pixel units. The gate lines and data lines are required to have lower resistance as the size of the display device increases and the demand for a display performance enhances. At present, commonly used aluminum wirings can not meet requirements for the display performance due to high resistivity. Copper has much lower resistivity than aluminum, and therefore it will be a main selection of using copper for gate lines and data lines in future.
However, copper ions have relatively high penetrability and can easily diffuse into an amorphous silicon or silicon layer configured for an active layer of the thin film transistor, for example. In addition, copper ions, which will be generated during etching metallic conductive layers or striping off photoresist, may also penetrated into the amorphous silicon layer, which may influence performance of the amorphous silicon layer (such as a thin film transistor). In addition, silicon ions and the other metallic ions may also easily diffuse into a copper conductive structure so that the resistivity of the copper conductive structure is increased and resistance against chemical corrosion thereof is reduced.